Looks like the pilot got caught in a thermal and the envelope ripped. The fire only started after the ship was doomed and the deflated fabric hit the burner. Normally balloon or blimp in this situation would quickly turn into a 100% deflated streamer with a zero chance of survival for anyone on board. The fact that it somehow managed to hold onto some air in the tail segment created enough drag to allow the pilot to survive the impact and escape the fire before the propane tanks exploded. That's some pretty extreme good luck!